This invention relates to devices for determining deviation of well bores and, more particularly, to a well tool which can measure the degree of deviation and transmit a signal to the surface indicating the amount of deviation so that an operator can take corrective action.
Many types of well bore deviation measuring devices have been developed. Some of them employ electronic sensors such as, for example, mercury reservoirs and electronic circuitry for determining and measuring well bore deviation and transmitting a signal to the surface by means of wires running through the drill string. Examples of such devices are shown in U.S. Pat. Nos. 3,791,043; 3,791,042; 3,789,510; 3,400,464; 3,252,225; and 2,665,497. In another type of device, a fluid flow control means used to measure deviation is interconnected with electronic circuitry for producing sonic signals which are transmitted to the surface through pipe sections which make up the drill string.
Other types of well bore deviation measuring tools have been developed which utilize means for periodically restricting the flow of drilling fluid for creating pressure pulses in the drilling fluid stream which are transmitted to the surface. These pressure pulses are varied in most cases by a pendulum-type valving mechanism. Examples of such devices are shown in U.S. Pat. Nos. 3,581,404; 3,470,620; 3,457,654; 3,431,654; 3,313,360; and 3,176,407. U.S. Pat. No. 4,120,097 teaches a device which transmits signals from a downhole sensor both in the drilling fluid and through the walls of pipe sections.